1. Field of the Invention
The present invention relates to a fluid knife for use with a treatment system used to clean or treat a workpiece. More specifically, the invention relates to a fluid knife having a purge feature to clear the nozzle.
2. Description of the Related Art
Prior to using a sheet of metal, such as steel or aluminum, in a variety of manufacturing processes and products, the sheet or workpiece as it is often referred to, either in the form of a continuous strip or a blank, is typically cleaned and/or treated. For instance, the workpiece may be plated, galvanized, descaled or pickled. Additionally, the workpiece may be washed, rinsed or otherwise treated in some other manner for subsequent operation.
Systems are available for cleaning or otherwise treating the workpiece. Such systems include a plurality of spray heads or brushes that contact the surface of the workpiece and in a cleaning operation, remove any foreign or particulate matter from the surface of the workpiece. Fluid knives have been used at the inlet and outlet of the apparatus to contain or confine the cleaning fluid within the apparatus. In addition, wringer rollers may be used to remove excess fluid from the workpiece and to drive the workpiece through the machine. The fluid used in the system is contained and is continually reused. Thus, the system operates in a closed environment wherein fluid exiting the fluid knives and the spray nozzles is collected, filtered and reused. While filtering removes most of the debris from the fluid, occasionally debris or other particulate matter finds its way into the fluid knife and becomes lodged in the opening of the fluid knife. When debris becomes lodged in the opening, it prevents fluid from exiting the fluid knife. Blockage of the nozzle opening causes streaking on the workpiece and also allows unwanted material to escape the enclosure. Additionally, if the fluid knife fails to maintain a continuous sheet of fluid striking the workpiece, cleaning or treatment fluid may escape through the gap created by the blockage.